This invention relates to toasters and, more particularly, to a high speed toaster which will toast bread slices at a rate which is twice as fast as commercially available toasters.
Conventional toasters typically employ spaced heating elements which comprise resister wires mounted on or wrapped about planar insulating sheets. Other arrangements include coiled resisters mounted by insulators to form a planar zig zag pattern on the sides of the bread to be toasted. The pattern formed by the resistance wires generally comprises the entire surface area of the bread faces. Reflectors are mounted to direct the radiant heat toward the bread surface.
Bread is placed in a movable carriage and is manually lowered between the planar heating elements against the bias of a spring. A locking mechanism holds the carriage in this position for a pre-selectable period of time until the bread has reached a desired degree of browness. A bimetallic sensor that deflects from heat activates a circuit to release the latching trigger and permit the carriage to move to an upper non toasting position. When the carriage is moved to the latter position the heating elements are de-energized.
These prior art toasters tend to dissipate much of the radiant heat energy rather than concentrate such energy on the bread to be toasted. Furthermore, after each cycle the bimetallic latching element must cool to a degree which is sufficient to lock the carriage in its downward toasting position. These factors contribute to a relatively slow toasting cycle or series of toasting cycles.
When used in the following description and claims, the term bread is intended to cover bread slices and a wide variety of like comestibles, including waffles and bagels.
This invention provides a toaster having a linear heat source which scans the surface of the bread in a first pass and at a rate which is sufficient to drive moisture from at least the surface of the bread, but which is insufficient to significantly darken the surface. The surface of the bread is then progressively traversed with the linear heat source in a second pass at a rate which is sufficient to darken and toast the surface to a desired degree.
According to one aspect of this invention, the linear heat source comprises a ceramic rod wound with a nichrome resistance wire. The linear heat source is provided with a semi cylindrical reflector which closely conforms to the heat source to focus the radiant energy on a narrow surface area of the bread to be toasted. A pair of such linear heat sources are mounted parallel to each other and horizontally adjacent the upper ends of a bread carriage guide. The bread carriage is mounted between the guides and is adapted to lower and raise bread slices mounted thereon between the parallel heat sources. The carriage is reciprocally driven by a chain and sprocket arrangement which is reversibly driven by a dc motor.
More specifically, this invention comprises a toaster housing having at least one slot opening to receive the bread to be toasted. A holding carriage is movable relative to the slot opening between a first position adjacent the opening to a second position spaced from the opening. A drive motor drives the carriage through a chain drive transmission and moves the carriage from the first position to the second position and from the second position back to the first position. A first switch is responsive to movement of the carriage to the second position to reverse the travel of the carriage from the second position to the first position. A second switch is responsive to movement of the carriage to the first position to de-energize the motor and terminate carriage travel. A substantially linear heat source is adjacent the first position and extends transversely across the path of travel of the carriage so that the bread passes the linear heat source as the carriage travels from the first position to the second position, and again passes the linear heat source as the carriage moves from the second position back to the first position.
According to another aspect of this invention the toaster includes a conventional carriage which is manually operated to a down or toasting position against the bias of a return spring. The carriage is latched in this position by a solenoid operated latching member. Linear heat sources are mounted in a vertical position on a chain driven carriage which is driven by a reversing dc motor. With the carriage in a down and latched position, the linear heat sources traverse opposite faces of the bread in opposite directions in a first pass to drive moisture from at least the surfaces of the bread and then traverse the surfaces in an opposite direction in a second pass at a rate which is sufficient to darken and toast the surface to a desired degree.
In each embodiment, opposite sides of the toaster are provided with transparent glass panels so that the toasting operation may be observed.